Question

activity b (continued from previous page)

1. classify: with the gizmo, test and categorize the remaining molecules. report your findings.

polar molecules nonpolar molecules
did the polarity of any of these molecules surprise you? explain.

1. explain: drag the ccl₄ molecule into the simulation area.

a. does this molecule contain polar or nonpolar bonds?
b. turn on the electric field. why do you think the molecule does not rotate in this field?
if a molecule is symmetrical, the effect of the partial charges on either side cancel out. in this case, even though it contains polar bonds, the molecule as a whole may be nonpolar.
c. what other nonpolar molecule contains polar bonds?

1. challenge: drag the ocl₂ molecule into the simulation area. turn on show valence electrons. what do you notice at the very top of the oxygen atom, and how does this feature explain why the molecule is polar?

in an ocl₂ molecule, the top of the oxygen atom contains two lone pairs of electrons. this gives the oxygen end of the molecule a slight negative charge and the chlorine end a slight positive charge.

Explanation:

Step1: Analyze CCl₄ bond - polarity

The C - Cl bonds in CCl₄ are polar due to the electronegativity difference between carbon and chlorine. But the molecule is tetrahedral and symmetrical, so the bond - dipoles cancel out.

Step2: Answer 4A

The CCl₄ molecule contains polar bonds.

Step3: Answer 4B

The CCl₄ molecule is non - polar overall because it is symmetrical (tetrahedral). The individual bond dipoles cancel each other out. So, when an electric field is turned on, there is no net dipole moment to cause rotation.

Step4: Answer 4C

Another non - polar molecule with polar bonds is CO₂. The C=O bonds are polar, but the linear geometry of CO₂ makes the molecule non - polar as the bond dipoles cancel.

Step5: Analyze OCl₂

In an OCl₂ molecule, the oxygen atom has two lone pairs of electrons at the top. These lone pairs create an asymmetrical electron - cloud distribution around the oxygen atom.

Step6: Answer 5

The two lone pairs of electrons on the oxygen atom in OCl₂ create an asymmetrical distribution of charge. This gives the oxygen end a slight negative charge and the chlorine end a slight positive charge, making the molecule polar.

Answer:

4A. Polar bonds
4B. The molecule is non - polar overall due to symmetry (tetrahedral shape), so individual bond dipoles cancel and there is no net dipole moment to cause rotation in an electric field.
4C. CO₂

1. There are two lone pairs of electrons at the top of the oxygen atom. These lone pairs create an asymmetrical charge distribution, making the oxygen end slightly negative and the chlorine end slightly positive, thus making the molecule polar.